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/*=========================================================================
*
* Copyright NumFOCUS
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* https://www.apache.org/licenses/LICENSE-2.0.txt
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
*=========================================================================*/
#ifndef itkWindowedSincInterpolateImageFunction_hxx
#define itkWindowedSincInterpolateImageFunction_hxx
#include "itkMath.h"
namespace itk
{
// Constant definitions for functions
namespace Function
{
template <unsigned int VRadius, typename TInput, typename TOutput>
const double CosineWindowFunction<VRadius, TInput, TOutput>::m_Factor = itk::Math::pi / (2 * VRadius);
template <unsigned int VRadius, typename TInput, typename TOutput>
const double HammingWindowFunction<VRadius, TInput, TOutput>::m_Factor = itk::Math::pi / VRadius;
template <unsigned int VRadius, typename TInput, typename TOutput>
const double WelchWindowFunction<VRadius, TInput, TOutput>::m_Factor = 1.0 / (VRadius * VRadius);
template <unsigned int VRadius, typename TInput, typename TOutput>
const double LanczosWindowFunction<VRadius, TInput, TOutput>::m_Factor = itk::Math::pi / VRadius;
template <unsigned int VRadius, typename TInput, typename TOutput>
const double BlackmanWindowFunction<VRadius, TInput, TOutput>::m_Factor1 = itk::Math::pi / VRadius;
template <unsigned int VRadius, typename TInput, typename TOutput>
const double BlackmanWindowFunction<VRadius, TInput, TOutput>::m_Factor2 = 2.0 * itk::Math::pi / VRadius;
} // end namespace Function
template <typename TInputImage,
unsigned int VRadius,
typename TWindowFunction,
typename TBoundaryCondition,
typename TCoordRep>
void
WindowedSincInterpolateImageFunction<TInputImage, VRadius, TWindowFunction, TBoundaryCondition, TCoordRep>::
SetInputImage(const ImageType * image)
{
// Call the parent implementation
Superclass::SetInputImage(image);
if (image == nullptr)
{
return;
}
// Set the radius for the neighborhood
Size<ImageDimension> radius;
radius.Fill(VRadius);
// Initialize the neighborhood
IteratorType it(radius, image, image->GetBufferedRegion());
// Compute the offset tables (we ignore all the zero indices
// in the neighborhood)
unsigned int iOffset = 0;
int empty = VRadius;
for (unsigned int iPos = 0; iPos < it.Size(); ++iPos)
{
// Get the offset (index)
typename IteratorType::OffsetType off = it.GetOffset(iPos);
// Check if the offset has zero weights
bool nonzero = true;
for (unsigned int dim = 0; dim < ImageDimension; ++dim)
{
if (off[dim] == -empty)
{
nonzero = false;
break;
}
}
// Only use offsets with non-zero indices
if (nonzero)
{
// Set the offset index
m_OffsetTable[iOffset] = iPos;
// Set the weight table indices
for (unsigned int dim = 0; dim < ImageDimension; ++dim)
{
m_WeightOffsetTable[iOffset][dim] = off[dim] + VRadius - 1;
}
// Increment the index
++iOffset;
}
}
}
template <typename TInputImage,
unsigned int VRadius,
typename TWindowFunction,
typename TBoundaryCondition,
typename TCoordRep>
void
WindowedSincInterpolateImageFunction<TInputImage, VRadius, TWindowFunction, TBoundaryCondition, TCoordRep>::PrintSelf(
std::ostream & os,
Indent indent) const
{
Superclass::PrintSelf(os, indent);
os << indent << "OffsetTable: " << m_OffsetTable << std::endl;
os << indent << "WeightOffsetTable: " << m_WeightOffsetTable << std::endl;
}
template <typename TInputImage,
unsigned int VRadius,
typename TWindowFunction,
typename TBoundaryCondition,
typename TCoordRep>
auto
WindowedSincInterpolateImageFunction<TInputImage, VRadius, TWindowFunction, TBoundaryCondition, TCoordRep>::
EvaluateAtContinuousIndex(const ContinuousIndexType & index) const -> OutputType
{
IndexType baseIndex;
double distance[ImageDimension];
// Compute the integer index based on the continuous one by
// 'flooring' the index
for (unsigned int dim = 0; dim < ImageDimension; ++dim)
{
baseIndex[dim] = Math::Floor<IndexValueType>(index[dim]);
distance[dim] = index[dim] - static_cast<double>(baseIndex[dim]);
}
// Position the neighborhood at the index of interest
Size<ImageDimension> radius;
radius.Fill(VRadius);
IteratorType nit(radius, this->GetInputImage(), this->GetInputImage()->GetBufferedRegion());
nit.SetLocation(baseIndex);
// Compute the sinc function for each dimension
double xWeight[ImageDimension][2 * VRadius];
for (unsigned int dim = 0; dim < ImageDimension; ++dim)
{
// x is the offset, hence the parameter of the kernel
double x = distance[dim] + VRadius;
// If distance is zero, i.e. the index falls precisely on the
// pixel boundary, the weights form a delta function.
if (distance[dim] == 0.0)
{
for (unsigned int i = 0; i < m_WindowSize; ++i)
{
xWeight[dim][i] = static_cast<int>(i) == VRadius - 1 ? 1 : 0;
}
}
else
{
// i is the relative offset in dimension dim.
for (unsigned int i = 0; i < m_WindowSize; ++i)
{
// Increment the offset, taking it through the range
// (dist + rad - 1, ..., dist - rad), i.e. all x
// such that itk::Math::abs(x) <= rad
x -= 1.0;
// Compute the weight for this m
xWeight[dim][i] = m_WindowFunction(x) * Sinc(x);
}
}
}
// Iterate over the neighborhood, taking the correct set
// of weights in each dimension
using PixelType = typename NumericTraits<typename TInputImage::PixelType>::RealType;
PixelType xPixelValue{};
for (unsigned int j = 0; j < m_OffsetTableSize; ++j)
{
// Get the offset for this neighbor
unsigned int off = m_OffsetTable[j];
// Get the intensity value at the pixel
PixelType xVal = nit.GetPixel(off);
// Multiply the intensity by each of the weights. Gotta hope
// that the compiler will unwrap this loop and pipeline this!
for (unsigned int dim = 0; dim < ImageDimension; ++dim)
{
xVal *= xWeight[dim][m_WeightOffsetTable[j][dim]];
}
// Increment the pixel value
xPixelValue += xVal;
}
// Return the interpolated value
return static_cast<OutputType>(xPixelValue);
}
} // namespace itk
#endif
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